Method for the fabrication of a “lab on chip” from photoresist material for medical diagnostic applications

ABSTRACT

The present invention relates to a device for performing immuno assays (“biochip” or “lab on chip” respectively), a procedure for its fabrication and the use of the device for performing immuno assays. Furthermore the present invention relates to the use of a photo lithographically patternable dry film photo resist based on a material with functional chemical groups for the immobilization of biomolecules.

This application is the national stage of PCT/EP02/08724, filed Aug. 5,2002, which in turn claims foreign priority to foreign applicationGermany 10139742.9, filed Aug. 13, 2001.

The present invention relates to a device for performing immuno assays(“biochip” or “lab on chip”), a method for its fabrication, and the useof such device for performing immuno assays, e.g. EIA and ELISA.Furthermore, the present invention relates to the use of photolithographically patternable dry film photo resist based on a materialwith functional chemical groups for the immobilization of biomolecules.

In the life sciences and in medical diagnostics the detection of(bio)chemical reactions, i.e. the detection of biologically relevantmolecules in a defined material to be analyzed, is of major importance.In this context the development of so called biochips is permanentlypropelled. Biochips typically are made from miniaturized hybridfunctional elements comprising biological and technical components,especially biomolecules on a surface (outside surface and/or insidesurface) used as specific (biomolecular) interaction partners.Frequently the structure of these functional elements comprise columnsand rows, forming the so called “chip-arrays”. Since thousands ofbiological or biochemical functional elements may be arranged on onechip, those chips are commonly fabricated using micro technologies.Biological and biochemical functional elements that can be used are inparticular DNA, RNA, PNA, (using nucleic acids and their chemicalderivatives e.g. single strands, triplex structures or combinations ofthose can be used), saccharides, peptides, proteines (e.g. antibodies,antigens, receptors), derivatives from combinatorial chemistry (e.g.organic molecules), cellular components (e.g. organelles), cells,multicellular organisms and cell assemblies.

Typically biochips comprise a 2D-base surface for the coating withbiological oder biochemical functional materials. The base surfaces maye.g. also be formed by walls of one or more capillaries or channels,respectively. An extension of the geometry is a 3D-structure, where theanalysis and also the manipulation or control respectively of reactionscan be performed in a 2D-arrangement. Current state of the arttechnologies available for the fabrication of biochips typically requirea chemical functionalization of the micro structure surfaces before thecoupling or binding of the biological or biochemical functionalelements. In particular, this can be achieved by activation ofphotosensitive groups in predefined locations of a substrate surface bymeans of localized light exposure of the substrate using an exposurematrix (see e.g. DE 199 40 752 A1). But the chemical functionalizationof the micro structured surfaces required for the immobilization of thebiomolecules aggravates production requirements for the fabrication ofsuch biochips considerably, making such techniques not only littlereliable but also very cost ineffective. Immobilization of thebiomolecules using adsorption techniques also generates a huge effortfor the surface coating.

Thus, the object of the present invention is to provide a simple,flexible, and cost effective method for the fabrication of so called“lab on chips” or “biochips”, that especially eases the localizedlinking of biological or biochemical functional elements, namely itshould avoid the problems associated with the chemical functionalizationof the micro structure surface required for the localized linking ofbiological or biochemical functional elements.

This object is solved by the embodiments as characterized in the claims.

In particular, there is provided a method for the fabrication of adevice for performing immuno assays, comprising:

-   (a) providing a micro structured substrate having predefined    indentations and/or through holes,-   (b) applying at least one layer of a dry film photo resist material    with functional chemical groups onto said substrate,-   (c) light exposing the dry film photo resist using a photo mask with    a predefined pattern,-   (d) developing the dry film photo resist layer,-   (e) repeating step (b) and step (c) using a photo mask with a    different predefined pattern and step (d), so that substrate and dry    film photo resist material form a capillary structure or capillary    channel structure, respectively, with at least one inlet and outlet,-   (f) localized immobilizing biomolecules to at least one region of    the inner surfaces of the dry film photo resist material channel    structure generated in step-   (e) by chemical coupling via the functional groups of the dry film    photo resist material, wherein a device for performing immuno assays    is obtained.

The present invention presents a novel technology platform for the costeffective, flexible, and reliable fabrication of devices, that isparticularly useful for performing immuno assays (so called “lab onchips” or “biochips”).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an example scheme showing the fabrication of a capillarychannel system according to the present invention.

FIG. 2 is an example scheme showing the procedure for performing anELISA using a capillary channel system according to the presentinvention.

The dry film photo resist materials used in the method of the presentinvention are based on photo patternable polymers that comprisefunctional chemical groups which are able to form a chemical link withrespective biomolecules. Preferably a dry film photo resist based on anegative photo resist is used in the method according to the presentinvention. In particular dry film photo resists based on polymericmaterials comprising functional groups selected from carboxylic acids,carboxylic acids anhydrids, carboxylic acid chlorides, aldehydes,glyoxals, N-hydroxy succinimide esters, hydrazides, imidates,isothiocyanates, isocyanates, maleinimides, halogenquinones, epoxides,aziridines, acylazides, phenoles, amino groups, thiol groups, hydroxylgroups, sulfhydryl-reactive bromium and iodine, and biotin groups.Preferably, the chemical functional groups are thiol groups (—SH) andgroups derived therefrom as e.g. pyridyl thio groups, carboxylic acidgroups (—COOH) and groups derived therefrom such as e.g. carboxylic acidanhydride groups like maleic acid anhydride or succinic acid anhydride,imide ester groups such as e.g. N-hydroxy-succinimide ester groups, andcarboxylate groups. Especially preferred are carboxylic acid groups. Ina preferred embodiment of the present invention the dry film photoresist is based on a mixture of polymers and optionally oligomers and/ormonomers, wherein at least one of the polymers, oligomers or monomerscomprises thiol-, carboxylic acid-, anhydride-, acid-amide- or imideester groups, preferable acrylic acid-, methacrylic acid-, maleic acidanhydride-, maleic acid imide- or N-hydroxy succinimide ester groups.The polymers used in such mixture may be block polymers, copolymers orgraft copolymers, in particular copolymers, preferably random orblock-copolymers which preferably comprise carboxylic acid-, anhydride-,acid amide- or imide ester groups. For example, photo resist materialson the basis of styrene/maleic acid anhydride-copolymers can bementioned. Of course such mixture may comprise additional additives ase.g. fillers, cross linkers, plasticizers, and photo initiators, as wellknown to an expert in the field of dry film photo resists. In the courseof the present invention, there is included the mixing or compounding ofan aforementioned dry film photo resist material based on polymers witha monomer or oligomer, that on the one side is capable of beingincorporated into the polymer network in the light induced cross linkingreaction and on the other side comprises one of the aforementionedfunctional chemical groups which are capable to form a chemical linkwith respective biomolecules. Examples are γ-malein imido butyricacid-N-hydroxy succinimide, γ-malein imido capronic-acid-N-hydroxysuccinimide oder N-acryloxy succinimide.

Dry Film Photo Resist Materials useful in the Present Invention are e.g.Vacrel® or Riston®, Both Manufactured by Dupont

Since already the photo resist material that is used in combination withthe substrate to fabricate the capillary structures by means of a photolithographic process, is comprising functional chemical groups, thesurface of the capillary channel system made from this dry film photoresist comprises, as the material itself, a high concentration offunctional groups, in particular free carboxylic acid groups, enablingpermanent chemical immobilization of biomolecules to this surface.Processing of the dry film resist material can be done especiallyadvantageous using printed circuit board technologies to fabricatecorresponding micro structures, namely channels and capillaries,respectively.

The substrate or carrier with predefined micro structured indentationsand/or through holes can be a substrate for printed circuit boards orfor semiconductors, a glass substrate or a polymer substrate, or also anon-patterned or already patterned dry film photo resist material. Thepredefined indentations and/or through holes can be made by e.g. usingconventional photo lithographic processes and etching processes. In caseof an already patterned dry film photo resist material this can beachieved in the preceding patterning process.

By repeated lamination and photo patterning using different photo masks,closed capillary structures or at least parts of channels orcapillaries, respectively, comprising at least one inlet and one outlet,can be fabricated by the method according to the present invention.Typical dimensions of such channel structures produced in step (e)according to the method of the present invention are e.g. heights from10 to 100 μm, widths of 10 to 500 μm and lengths of 10 to 1000 mm. Thechannels may be straight or meandering and continuous or comb-shapedarranged. Furthermore they can be arranged in one or two dimensionalarrays, in one plane or stacked in multiple planes. Accordingly, themethod according to the present invention also allows the fabrication ofthree dimensional arrays. If the capillary structure(s) is/are stackedin multiple planes, the capillaries may be connected by verticalchannels. Zero dimensional (a single capillary), one dimensional or twodimensional arrays may be vertically stacked or can also beinterconnected fluidically in such configuration by means of verticalopenings.

In one embodiment of the method according to the present invention thefunctional chemical groups can be activated before step (f). If the dryfilm photo resist is based on polymers comprising carboxylic acidgroups, this activation can be e.g. done by reaction with a carbodiimidecompound such as dicyclohexylcarbodiimid (DCC). Such carbodiimidesolution can be pumped through at least parts of the channel system,wherein the carboxylic acid groups are activated. Subsequently, the thusactivated inner surfaces are coated at those sites of the channelsystem, which are formed by the dry film photo resist material, with therespectively selected biomolecules, such as e.g. an antibody, bychemical link with them.

In one embodiment of the method according to the present invention step(f) can be carried out by using immersion or pouring processes withsubsequent sealing of the capillary structure with a top layer of atleast one dry film photo resist. Alternatively, with exception of thechannels provided as inlets and outlets, the capillary structure can beclosed in the course of step (e) and subsequently step (f) can becarried out by using pumping processes. Furthermore in step (f) also asolution of biomolecules can be delivered to one or more capillaries ofthe capillary structure obtained in step (e) with at least one needle orneedle arrangement utilizing capillary forces. For example, an excess offluid can be delivered by a needle or an instrument comprising multipleneedles to a vertical opening of such a capillary in a way that thiscapillary fills with this fluid by capillary forces. After the desiredreaction time the fluid can be removed from the capillary by applyingexcess pressure. An also advantageous embodiment uses openings in thecapillaries solely used for the immobilization of the biomolecules thatis closed after the immobilization, e.g. with a dry film resist or apressure sensitive adhesive.

Useful biomolecules for the localized and selective direct chemicalcoupling of step (f) to the functional groups of the dry film photoresist material to at least one region of the inner surface formed bythe dry film photo resist material capillary structure made in step (e)are in particular DNA, RNA, PNA, (using nucleic acids and their chemicalderivatives e.g. single strands, triplex structures or combinations ofthose can be used), saccharides, peptides, proteines (e.g. antibodies,antigens, receptors), derivatives from combinatorial chemistry (e.g.organic molecules), cellular components (e.g. organelles), cells,multicellular organisms and cell assemblies. If the device is intendedto be used for performing EIA or ELISA, biomolecules used are inparticular specific antibodies immobilized in step (f) localized andselective by chemical coupling to the functional groups of the dry filmphoto resist material to at least one region of the inner surface formedby the dry film photo resist material capillary structure obtained instep (e).

In a preferred embodiment of the present invention at least onecapillary of the capillary structure is made as affinity capillary byimmobilization of biomolecules and at least one capillary of thecapillary structure is made as amplification capillary. The function ofthe amplification capillary is basically to amplify the chemical signalgenerated in the affinity capillary, by passing an analyte or samplesolution, as e.g. a serum sample, by a cycling process. Preferably thechannels of the amplification capillary are fabricated simultaneouslywith the affinity capillary, wherein affinity capillary andamplification capillary can be directly connected with each other. Oneamplification capillary can be provided for one affinity capillary.Multiple affinity capillaries can end into one amplification capillary,alternatively one affinity capillary can end in multiple amplificationcapillaries. Moreover, affinity- and amplification capillary can bearranged in one plane or fabricated separately and stacked verticallyfor use.

When passing a fluid to be analyzed (analyte) the chemical signalresulting from the interaction with the localized immobilizedbiomolecules is preferably measured electrochemically, preferablyamperometrically, or spectrophotometrically or fluorescencespectrophotometrically.

If the chemical signal is e.g. generated glucose—if the biomoleculeimmobilized in step (f) localized and selective by direct chemicalcoupling to the functional groups of the dry film photo resist materialto at least one region of the inner surface formed by the dry film photoresist material capillary structure obtained in step (e) is e.g.alkaline phosphatase and the analyte passed through the capillarystructure contains glucose-6-phosphate—the resulting chemical signal,i.e. in the example glucose, can be converted multiple times, using oneor more amplification capillaries, in a cyclic process according to thefollowing scheme and accordingly amplified depending on the number ofcycles:

In each cycle one molecule, i.e. in the example glucose, is formed. Inthe preceding exemplary reaction scheme hydrogen peroxide (H₂O₂) isformed that is oxidized on an electrode and quantified in this way.

The degree of the signal amplification induced by the amplificationcapillary basically depends on the velocity of the cyclic reactions(approx. the product of the respective enzymatic activities—in thepreceding example GOD and GDH), the number of cycles and the glucoseconcentration.

Preferably, the amplification capillary is functionalized byimmobilization of at least two enzymes that convert the chemical signalof the affinity capillary by a chemical cycling process into anamplified chemical signal. The immobilization of the enzymes to at leastone region of the inner surface formed by the dry film photo resistmaterial can either be done as the functionalization of the affinitycapillary by chemical linking to the functional groups of the dry filmphoto resist material or by encapsulation into membranes or gels thatcover one or more areas of the inner surfaces of the capillary. Thesemembranes or gels can also advantageously be fabricated photolithographically. The immobilization of the enzymes by gel entrapmentallows for even higher volume activities. Of course such gel isoccupying only a part of the channels cross section to allow a flow ofanalyte. Preferably the gel is bound by chemical links to at least oneregion of the inner surface of the channel system formed by the dry filmphoto resist material. This can be achieved by radical initiated crosslinking of the gel in the capillary, wherein still remainingpolymerizable groups of the dry film photo resist material participatein the radical reaction.

Beside such “direct” analysis procedures, of course, also “indirect”immunological analysis of biologically active substances, such as EIA(enzyme-immunoassay) and ELISA (enzyme linked immunosorbent assay) canbe performed according to the present invention, as exemplary shown inFIG. 2. For example the reaction between an antigen to be measured in asample solution and a specific antibody, that is immobilized in step (f)localized and selective by chemical coupling to the functional groups ofthe dry film photo resist material to at least one region of the innersurfaces formed by the dry film photo resist material capillarystructure produced in step (e), can be detected by a subsequentmeasurement of preferably an enzyme bound to the antigen (e.g.horseradish peroxidase or other plant, bacterial or animal enzymes). Ingeneral in an EIA the specificity of the antigen-antibody-reaction iscoupled with an enzymatic reaction, by either using antibody- orantigen-enzyme-conjugates, that are measured via their enzymaticactivity photometrically, fluorometrically or electrochemically afteraddition of a suitable substrate, wherein again an amplificationcapillary may be used for signal amplification. In the presentinvention, for ELISA the specific antibody against the antigen to bemeasured is immobilized in step (f) localized and selective by chemicalcoupling to the functional groups of the dry film photo resist materialto at least one region of the inner surface formed by the dry film photoresist material capillary structure produced in step (e). To saidantibody the antigen of the sample solution, e.g. a serum sample, bindsand the remaining sample is washed off. Subsequently a second antibodycoupled to a fully functional enzyme is added, binding to the alreadybound antigen. The enzyme-activity of the enzyme coupled via theantibody-antigen-antibodies conjugate to the capillary wall can bemeasured after addition of a suitable substrate, wherein also one ormore amplification capillaries, as exemplified above, may be used.

A further subject matter of the present invention relates to a devicefor performing immuno assays comprising at least one substrate andprovided thereon at least one dry film photo resist polymer materialcomprising functional chemical groups, wherein substrate and dry filmphoto resist polymer material form together a capillary structure withat least one inlet and one outlet, wherein biomolecules are chemicallybound, via the functional groups of the dry film photo resist polymermaterial, to the inner surfaces of the capillary structure formed by thedry film photo resist material. The dry film photo resists, especiallythose based on negative photo resists, are based on the aforementionedphoto patternable polymers, which comprise the aforementioned chemicalgroups. Especially, there are used dry film photo resists based onpolymeric materials comprising functional groups selected fromcarboxylic acids, carboxylic acids anhydrids, carboxylic acid chlorides,aldehydes, glyoxals, N-hydroxy succinimide esters, hydrazides, imidates,isothiocyanates, isocyanates, maleinimides, halogenquinones, epoxides,aziridines, acylazides, phenoles, amino groups, thiol groups, hydroxylgroups, sulfhydryl-reactive bromium and iodine and biotin groups.Preferably, the chemical functional groups are thiol groups (—SH) andgroups derived from them such as e.g. pyridyl thio groups, carboxylicacid groups (—COOH) and groups derived from them such as e.g. carboxylicacid anhydride groups like maleic acid anhydride or succinic acidanhydride, imide ester groups as e.g. N-hydroxy-succinimide estergroups, and carboxylate groups.

In a preferred embodiment of the present invention the dry film photoresist is based on a mixture of polymers and optionally oligomers and/ormonomers and additional additives such as e.g. fillers, cross linkers,plasticizers, and photo initiators, wherein at least one of thepolymers, oligomers or monomers comprises thiol-, carboxylic acid-,anhydride-, acid-amide- or imide ester groups, preferable acrylic acid-,methacrylic acid-, maleic acid anhydride-, maleic acid imide- orN-hydroxy succinimide ester groups. The polymers used in such mixturemay be block polymers, copolymers oder graft copolymers, in particularcopolymers, preferably random or block copolymers which preferablycomprise carboxylic acid-, anhydride-, acid amide- or imide estergroups. In the present invention, there is also included the mixing orcompounding of an aforementioned dry film photo resist material with amonomer or oligomer, that is on the one side capable of beingincorporated into the polymer network in the light induced cross linkingreaction and on the other side comprises one of the aforementionedfunctional chemical groups which are capable to form a chemical linkwith respective biomolecules. Examples are γ-malein imido butyricacid-N-hydroxy succinimide, γ-malein imido capronic-acid-N-hydroxysuccinimide oder N-acryloxy succinimide.

Dry Film Photo Resist Materials useful in the Present Invention are e.g.Vacrel® Oder Riston®, Both Manufactured by Dupont

The substrate or carrier with predefined micro structured indentationsand/or through holes can be a substrate for printed circuit boards orfor semiconductors, a glass substrate or a polymer substrate, or also anon-patterned or already patterned dry film photo resist material. Asbiomolecules DNA, RNA, PNA, (using nucleic acids and their chemicalderivatives e.g. single strands, triplex structures or combinations ofthose can be used), saccharides, peptides, proteines (e.g. antibodies,antigens, receptors), derivatives from combinatorial chemistry (e.g.organic molecules), cellular components (e.g. organelles), cells,multicellular organisms and cell assemblies, can particularly bementioned. If the device is intended to be used for performing EIA orELISA, biomolecules used are in particular specific antibodiesimmobilized in step (f) localized and selective by chemical coupling tothe functional groups of the dry film photo resist material to at leastone region of the inner surface formed by the dry film photo resistmaterial capillary structure made in step (e). In the device of thepresent invention preferably at least one capillary of the capillarystructure is made as affinity capillary by immobilization ofbiomolecules and at least one capillary of the capillary structure ismade as amplification capillary. The amplification capillary can e.g. befunctionalized by at least two enzymes.

In a preferred embodiment of the present invention the device comprisesat least two electrodes that can be provided for one capillary ormultiple capillaries simultaneously. The electrodes can be made as microelectrodes or micro electrode arrays. In this embodiment the arrangementof the electrodes enables the electrochemical detection for thequantification of the chemical signal from the affinity or amplificationcapillary, respectively. At least two electrodes are in contact with thefluid to be analyzed. The electrodes, either one or all of them, can befabricated or arranged, respectively, in the course of the fabricationof the channel system on the same carrier or substrate. Alternativelythe electrodes, either one or all of them, can be fabricated separatelyfrom the capillaries and assembled in the course of the fabrication ofthe device or when the device is to be used. Either one such detectionunit comprising at least two electrodes can be used for one capillary oralternatively it is used for multiple capillaries. Especiallyadvantageous is amperometric measurement, where the chemical signal thate.g. is correlated to the concentration of the produced chemicalspecies, is electrochemically converted at one or more electrodes whichare polarized to a constant potential versus the solution resulting in ameasurable current proportional to the concentration of said chemicalspecies. Advantageously the electrodes are made as micro electrodes,e.g. also enzyme electrodes, or micro electrode arrays. Furthermore thechemical signal from the affinity or amplification capillary,respectively, can not only be directly converted at one or more of theseelectrodes, but can also, by means of enzymes entrapped in membranes ontop of this electrode, become subjected to a chemical amplification.Moreover, one or more additional electrodes, where the describeddetection processes do not take place and whose signal is used to obtaina difference signal with the detecting electrode(s), by what the signalto noise ratio can be increased, can be implemented.

Alternatively also optical, namely spectrophotometric detection methodscan be provided, especially such using fluorescence measurement. Forthis approach at least one part or the channel structure comprises anoptical transparent lid.

For the use of the device according to the present invention initiallythe fluid to be analyzed is brought into the capillary system, namelyinto the at least one affinity capillary. The flow can either beinterrupted for a certain time, to allow the affinity reaction, as e.g.antibody-antigen, to take place, or the flow is maintained for a certaintime to increase the sensitivity by providing the transport of a largeramount of the substance to be detected or analyzed, respectively. Aftera washing step the affinity capillary is loaded with a solution of adetection-biomolecule (protein, antibody, DNA, RNA), which comprisescatalytic activity e.g. by coupling with an enzyme (e.g. glucoseoxidase, horseradish peroxidase or other bacterial, plant or animalenzymes). After the desired incubation time has elapsed, usually washingis carried out once again and the affinity capillary is loaded with asolution comprising a substance that is converted as a result of thecatalytic activity of the bound biomolecule. Quantification of the assaycan then be performed either by passing this solution continuouslythrough the affinity capillary and eventually through the amplificationcapillary and through the detection unit or alternatively keeping thesolution for the desired time in the affinity and/or the amplificationcapillary, resulting in a continuous accumulation of the species to bedetected, wherein the fluid volume of the affinity capillary may betransferred to the amplification capillary, where the solution alsoremains for the desired time and finally this fluid volume is pumpedinto the detection unit comprising electrochemical and/or photometricmeasurement units.

The device or carrier, respectively, for the procedure for themeasurement of an analyte according to the present invention is suitablefor performing immuno assays, especially for the immunologicaldetermination of biologically active substances in body fluids. Forexample the reaction between an antibody that is directly bound througha chemical link to the functional groups of the dry film photo resistmaterial to the inner surfaces of the capillary structure formed by thedry film photo resist material, and an antigen as a substance to bemeasured can be detected e.g. by the subsequent determination of anenzyme bound to said antigen or bound to the antibody. Such tests areuseful for the measurement of drugs, hormones, and proteins.

A further subject matter of the present invention relates to the use ofa photo lithographically patternable dry film photo resist based on amaterial comprising functional chemical groups for the immobilization ofbiomolecules. Preferably a dry film photo resist based on a negativephoto resist is used. Especially dry film photo resists based onpolymeric materials are employed, which contain functional groupsselected from carboxylic acids, carboxylic acids anhydrids, carboxylicacid chlorides, aldehydes, glyoxals, N-hydroxy succinimide esters,hydrazides, imidates, isothiocyanates, isocyanates, maleinimides,halogenquinones, epoxides, aziridines, acylazides, phenoles, aminogroups, thiol groups, hydroxyl groups, sulfhydryl-reactive bromium andiodine and biotin groups. Preferably the chemical functional groups arethiol groups (—SH) and groups derived from them such as e.g. pyridylthio groups, carboxylic acid groups (—COOH) and groups derived from themsuch as e.g. carboxylic acid anhydride groups like maleic acid anhydrideor succinic acid anhydride, imide ester groups such as e.g.N-hydroxy-succinimide ester groups, and carboxylate groups. Especiallypreferred are carboxylic acid groups. In a preferred embodiment of thepresent invention the dry film photo resist is based on a mixture ofpolymers and optionally oligomers and/or monomers and additionaladditives, as e.g. fillers, cross linkers, plasticizers, and photoinitiators, wherein at least one of the polymers, oligomers or monomerscomprises thiol-, carboxylic acid-, anhydride-, acid-amide- or imideester groups, preferable acrylic acid-, methacrylic acid-, maleic acidanhydride-, maleic acid imide- or N-hydroxy succinimide ester groups.The polymers used in such mixture may be block polymers, copolymers orgraft copolymers, in particular copolymers, preferably random or blockcopolymers, preferably comprising carboxylic acid-, anhydride-, acidamide- or imide ester groups. In the present invention, there is alsoincluded the mixing or compounding of an aforementioned dry film photoresist material based on polymers with a monomer or oligomer that is onthe one side capable of being incorporated in the polymer network in thelight induced cross linking reaction and on the other side comprises oneof the aforementioned functional chemical groups which are capable toform a chemical link with respective biomolecules. Examples are γ-maleinimido butyric acid-N-hydroxy succinimide, γ-malein imidocapronic-acid-N-hydroxy succinimide oder N-acryloxy succinimide.

1. A method for the fabrication of a device for performing immunoassayscomprising: (a) providing a micro structured substrate having predefinedindentations and/or through holes; (b) applying at least one layer of adry film photo resist material, wherein the dry film photo resistcomprises an outer surface facing away from the substrate and an innersurface facing toward the substrate, wherein the outer surface issubject to photo lithographic light and the inner surface comprisesfunctional chemical groups attached thereto; (c) light exposing the dryfilm photo resist using a photo mask with a different predefinedpattern; (d) developing the dry film photo resist layer; (e) repeatingstep (b) and step (c) using a photo mask with a different predefinedpattern and step (d), so that substrate and dry film photo resistmaterial form a capillary structure or capillary channel structure,respectively, with at least one inlet and outlet; and (f) localizedimmobilizing biomolecules to at least one region of the inner surface ofthe dry film photo resist material channel structure generated in step(e) by chemical coupling via the functional groups of the dry film photoresist material, wherein a device for performing immuno assays isobtained.
 2. The method according to claim 1, wherein the dry film photoresist is based on a negative photo resist.
 3. The method according toclaim 1 or 2, wherein the functional chemical groups are selected fromcarboxylic acids, carboxylic acids anhydrids, carboxylic acid chlorides,aldehydes, glyoxals, N-hydroxy succinimide esters, hydrazides, imidates,isothiocyanates, isocyanates, maleinimides, halogenquinones, epoxides,aziridines, acylazides, phenoles, amino groups, thiol groups, hydroxylgroups, sulfhydryl-reactive bromium and iodine and biotin groups,preferably thiol groups (—SH) and groups derived therefrom andcarboxylic acid groups (—COOH) and groups derived therefrom.
 4. Themethod according to claim 1, wherein the dry film photo resist is basedon a mixture of polymers and optionally oligomers and/or monomers,wherein at least one of the polymers, oligomers or monomers comprisesthiol-, carboxylic acid-, anhydride-, acid-amide- or imide ester groups,preferably acrylic acid-, methacrylic acid-, maleic acid anhydride-,maleic acid imide- or N-hydroxy succinimide ester groups.
 5. The methodaccording claim 1, wherein the functional chemical groups are carboxylicacid groups, which are activated before step (f).
 6. The methodaccording to claim 3, wherein the activation, if the functional groupsare carboxylic acid groups, and wherein activation of said carboxylicacid groups is carried out by reaction with a carbodiimide compound. 7.The method according to claim 1, wherein step (f) is performed by usingan immersion or pouring process and the channels of the capillarystructure are subsequently closed with either a top layer of at leastone dry film photo resist layer or with a self sealing film.
 8. Themethod according to claim 1, wherein in the course of step (e) thepredefined channels of the capillary structure are closed, with theexception of the channels provided as inlets and outlets, andsubsequently step (f) is performed by using pumping techniques.
 9. Themethod according to claim 1, wherein in step (f) a solution ofbiomolecules is delivered to one or more capillaries of the capillarystructure obtained in step (e) by means of at least one needle or anarrangement of needles utilizing capillary forces.
 10. The methodaccording to claim 1, wherein the biomolecules used in step (f) are DNA,RNA, PNA, saccharides, peptides, proteines, cellular components, cells,multicellular organisms and cell assemblies.
 11. The method according toclaim 1, wherein by binding of biomolecules, at least one capillary ofthe capillary structure is made as affinity capillary and at least onecapillary is made as amplification capillary.
 12. The method accordingto claim 11, wherein the amplification capillary is functionalized byimmobilization of at least two enzymes.
 13. The method according toclaim 12, wherein the immobilization of the enzymes to at least oneregion of the inner surface of the capillary structure formed by the dryfilm photo resist material, is carried out by chemical linking via thefunctional groups of the dry film photo resist material or by entrapmentinto a membrane that covers one or more of the inner surfaces of thecapillary structure.
 14. The method according to claim 13, wherein themembrane is fabricated photo lithographically.
 15. The method accordingto claim 1, wherein the chemical signal, generated due to theinteraction of the bound biomolecules with a passing fluid to beanalyzed, is measured electrochemically, preferably amperometrically, orfluorescence spectrophotometrically.